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Morphologies and Thermal Properties of Hydroxypropylated High-Amylose Corn Starch

¹CPFRR, School of Light Industry and Food, ERCPSP, South China University of Technology, Guangzhou, P.R. China. ²School of Materials Science and Engineering, South China University of Technology, Guangzhou, P.R. China. ³Commonwealth Scientific and Industrial Research Organisation, CMSE, Melbourne, Vic 3169, Australia. ⁴Corresponding author. Phone: +61 3 9545 2777. Fax: +61-3-95441128. E-mail: long.yu@csiro.au

High-amylose (80%) corn starch was modified by hydroxypropylation with different molar substitution (MS). The unique microstructure of high-amylose starch keeps its granules intact after hydroxypropylation. However, the microstructures and thermal properties strongly depend on the MS of hydroxypropylation. With increasing MS, the granule size was increased, which is partly due to disrupted granule structure, particularly in the amorphous region. Unlike normal starch, the modified high-amylose corn starch showed a narrow gelatinization range measured by differential scanning calorimetry (DSC), which can be explained by destruction of amylose-lipid complex. Internal microstructures and morphologies of hydroxypropylated starch were investigated using confocal laser scanning microscopy and to further explore the mechanism of chemical reaction and phase transitions.